Light metal alloy



lgg J. A. GANN LIGHT METAL ALLOY Original Filed OCT.. 27. 1921 BY @9a7 v,1 TTORNEYA Patented Aug. 7, 192

A tata au @ico JOHN A. GANN, F MIDLAND, MICHIGAN, ASSIGNOR TO THE DOWCHEMICAL COM- PANY, OF MIDLAND, MICHIGAN, A. CORPORATION 0F MICHIGAN.

LIGHT METAL ALLOY.

- Application led October 27, 1921, Serial No.'v510,794. Renewed August26, 1926.

The present improved alloy is one in which magnesium is the predominantelement, the object being to develop an alloy that will possess thecharacteristic lightness which is obtained by the use of magnesium inexcess of 80 per cent, while such alloy will be characterized by highstrength and high toughness, without sacrificing hardness unduly.

The field of use in the mechanical arts to lo which an alloy possessingthe lightness and physical characteristics enumerated above may beapplied is extensive and need not be described in detail for the purposein hand. Where hardness rather than softness may be i5 considereddesirable, as for example, when the metal is to be used in pistons ofinternal combustion engines, this characteristic may be improved ifdesired by adding one or more other metals in varying quantities, aswill be hereinafter explained, the present invention consisting of analloy of magnesium and tin with or without the addition of such furthermetals, together with the steps involved in the making of such alloyhereinau after fully described and particularly pointed out in theclaims. The annexed drawing and following description, it will beunderstoodset forth but several of the various ways in which theinvention may be carried out.

' In said annexed drawing The single ligure there appearing is adiagrammatic representation of certain physical properties discovered ina binary magnesium-tin alloy of the class in hand.

In such diagrammatic figure, the physical properties represented, itwill be noted, are

, the impact-toughness, hardness and tensile strength, the hardnessbeing determined by a@ the Brinell method and scaled to correspond withthe single blow impact-toughness. Such impact toughness drops veryrapidly with the addition of tin. The curve indicating this propertybecomes more nearly horizontal at higher percentages of added metal.

rlhe tensile strength, on the contrary, in-

creasesrapidly at first, then more slowly, and nally begins to fall ed,while the Brinell hardness increases slowly with the addition 5o of tinthroughout the major portion of the range under consideration. Forabinary alloy that will be properly balanced in respect 7to thecharacteristics in question, l prefer to use between 6 and 10 per centtin.

ce ACastings made from the resulting alloy,

Where between 6 and 10 er cent of tin is thus utilized, the balance eingmagnesium, will have a specific gravity from 1.80 to 1.90; tensilestrength, from 18000 to 20000 pounds per square inch; Brinell hardness,from 38 to 41; and single blow impact-toughness, from to 30. l

U Where the alloy is to be used for pistons 1n internal combustionengines, or under conditions involving similar strains and temperatures,I have found that the addition of a small proportion of aluminum isadvantageous to impart increased hardness and toughness to the resultingproduct. A satisfactory formula for such a ternary alloy using myimproved binary magnesium-tin alloy as a base, is as follows :-88 percent magnesium, 8 per cent tin, and 4 per cent aluminum, Still betterresults arey obtained for the particular field of use referred to by thefurther addition of a small proportion of copper or cadmium, asatisfactory formula iin such case being as follows, viz :-86 per centmagnesium, 8 per cent tin, 4 per cent aluminum and 2 per cent cadmium.

Even where the proportion of aluminum thus added is greater than that oftin, as in the following formula,` viz :-90 per cent magnesium, 8 percent aluminum and 2 per cent tin, the characteristics noted above ashaving been, discovered in the simple binary alloy of magnesium and tinwill be retained to a perceptible degree.

To make my improved alloy, a measured quantity of pure magnesium metalis first melted in a suitable pot along with the proper amount of a fluxthat, while heavier than such metal, will have proper surfacetension :topromptly and effectively coat the metal. As an example of such a flux,approximately equal parts of anhydrous magnesium chloride and sodiumchloride may be employed, and if the specific gravity of such fluxproves inadequate to oat the metal after it has been alloyed, a smallamount of barium chloride may be added. A small amount of the moltenmagnesium metal is then taken up in a ladle and all or a part of thetin, depending on the total percentage of the latter to be added to thebatch,v is first placed in such ladle and melted with the magnesiumtherein, thereby producing an alloy relatively high in tin. The contentsof the ladle are then gradually added to the Mtl main.-A body of moltenmagnesium, with the result that the tin will diffuse throughout the massand not drop through into the body of flux on which the lat-ter floatsand so be lost. As soon as the introduction of the tin alloy has beeneffected, the whole mass is Well puddled, and the operation may then beregarded as complete and-the molten alloy cast either into ingots ordirectly into the form of mechanical parts, such as pistons or the likefor which it is intended to be used.

Where either aluminum or cadmium, or both, are to be added to the binaryalloy in accordance with formulas such as hereinbefore set forth, therelatively small amount of such additional metal or metals may beseparately introduced in the same fashion as the tin, or they may be atonce added along with the tin in forming the preliminary alloy which issubsequently added to the main body of the molten magnesium metal,resulting in the product-ion of an alloy in which such magnesium is thepredominant ingredient. Again, in some cases, it may be moreadvantageous to add to lthe magnesium in the ladle a magnesium alloyrich in the alloying metal, instead of such metal by itself. p

For convenience in defining the relative proportions of the metals thatenter into the alloy, the magnesium may be referred to as presentin-.predominant amount, meaning an amount on the order of 80 per cent ormore of the total; while in referring to the presence of otherconstituents in substantial but relatively small amounts, it will beunderstood that amounts are meant on the order of those specified in theformulas hereinbefore set forth, due regard being given to the fact thatthe total of such other ingredients will decrease as the amount of thepredominant constituent is increased.

Other modes of applying the principle of my invention may be employedinstead of the one herein explained, change being made as regards thesteps herein disclosed or the ingredients employed in carrying out suchsteps, Aprovided the steps or ingredients not less than eighty nor morethan ninetynine and one-half per cent of magnesium,

and not more than twenty nor less than one half of one per lcentof tin.

2. As a new product, an alloy containing from ninety to ninety-four percent of magnesium, and from six to ten per cent of tin.

.3. As a new product, an alloy containing not less than eighty nor morethan ninetynine per cent of magnesium, not more than twenty nor lessthan one per cent of tin,

and aluminum in relatively small proportions.

4. As a new product, an alloy containing notless than eighty nor morethan ninetynine per cent of magnesium, not more than twenty nor lessthan one per cent and aluminum and cadmium in relatively smallproportions.

5. As a new product an alloy containing approximately the indicatedpercentages of the following metals, cent of magnesium, eight per centof tin and four per cent of aluminum.

6. The method of making a magnesiumtin alloy, which consists in firstinter-fusing the desired amount small quantity of magnesium, and thenadding the resulting alloy to th'e remaining quantity of magnesium inmolten state. i

7. The method of making .a magnesiumtin alloy, wherein predominates,which consists in iirst interfusing the desired amont of tin with arelatively small quantity of magnesium, where by an alloy'high in tin isproduced, and then adding such result-ing alloy quantity of magnesium.

Signed by me, this 24th day of October,

JOHN A. GANN.

of tin,

of tin with a relatively the magnesium largely to the remaining

